1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the device, more specifically, to a semiconductor device including a capacitor using a dielectric film, and a method of manufacturing the device.
2. Description of the Related Art
In recent years, development of a ferroelectric random access memory (FeRAM), which is a nonvolatile memory using a ferroelectric thin film, has been advanced.
For the FeRAM, ferroelectric materials such as PZT (Pb(ZrxTi1−x)O3), BIT(Bi4Ti3O12), and SBT(SrBi2Ta2O9) are used in a capacitor. All of these materials have a crystalline structure on the basis of a perovskite structure, whose basic structure is an oxygen octahedron. Different from a conventional Si oxide film, these materials do not have characteristic ferroelectricity in an amorphous state, and cannot therefore be used in amorphous. Therefore, processes for crystallization, such as a crystallizing heat treatment at a high temperature, and an in-situ crystallization process at the high temperature are required. In general, the temperature required for the crystallization is in a range of at least 400 to 700° C., depending on the material. Examples of a film forming method include an MOCVD process, a sputtering process, and a chemical solution deposition (CSD) process.
Moreover, a method of manufacturing a semi-conductor device using such ferroelectric thin film has been disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-260954.
The FeRAM using PZT which is a Pb compound as a typical ferroelectric material as described above essentially contains wear-out factors, and is therefore requested to include a conductive oxide material as an electrode. As the conductive oxide material, conductive perovskite oxide films such as an SrRuO3 film are used which have a satisfactory interface matching property with the perovskite oxide materials such as PZT.
However, when SrRuO3 containing an Ru element is employed to an electrode film, excess Pb reacts with Ru at a film interface between PZT and SrRuO3 and at a PZT grain boundary to form a conductive material (Pb2Ru2O7−x, and the like), which act as a leak path, and an increase of a leak current caused by the path leads to a characteristics deterioration problem.